Protein modifications related to phage resistance in a marine Roseobacter

The Roseobacter lineage is an important group of bacteria in the marine environment. Silicibacter pomeroyi DSS-3 has been used as a model strain for understanding the biological and ecological relevance of this group. Recently, a phage (Φ1) which infects S. pomeroyi DSS-3 was isolated in our laboratory. Mutants of DSS-3 that are resistant to phage Φ1 were also obtained. A comparison of the protein expression profiles of the wild type, DSS-3, and the phage Φ1-resistant mutant M1 identified a potential phage resistance response due to the modification of 4 highly expressed proteins. One of these 4 proteins was successfully identified via mass spectrometry, and matched a hypothetical protein (SPOA0343) in the S. pomeroyi DSS-3 genome. Although the type of protein modification has not yet been determined, our results suggest that bacteria could become resistant to phage infection via protein modification. Studies on phage resistance of S. pomeroyi DSS-3 could provide new insight into the complex relationship between marine bacteria and their viruses in the natural environment.